Note that we can also estimate the strength of interactions by using the Granger causality test [1]}. Although the Granger causality test only focuses on interactions, using our framework enables us to estimate the common frequency \(\omega _0\)  and the strength of interactions simultaneously.
We also remark that for \(N\ge 3\) , estimating the rigorous form of the PCF is challenging.
Thus, here, we focused on the strength of interactions.
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